1. Field of the Invention
The invention relates to a driving unit of a welding equipment capable of converting a rotary output of a motor into reciprocating motion of a pressure application shaft so that the pressure application shaft can operate a gun arm or a welding jig.
2. Related Art
There is a known driving unit of a welding equipment provided with a pressure application shaft to be driven by a motor as disclosed, for example, in Japanese Utility Model Registration No. 3042268 and Patent Laid-Open Publication No. 9-144834, wherein a screw shaft is provided on an output shaft extended from a motor by way of a gear and a screw provided on one end of the screw shaft is screwed with a nut formed on the pressure application shaft (hereinafter referred to as a first prior art).
There is a further known driving unit of a welding equipment provided with a pressure application shaft to be driven by a motor as disclosed, for example, in Japanese Patent Laid-Open Publication No. 7-290251, wherein a rotary shaft of a motor is made hollow and a screw shaft is forced to penetrate this hollow portion so that a screw formed on the screw shaft is screwed with a nut fixed to the rotary shaft (hereinafter referred to as a second prior art).
However, in the first prior art, since the screw shaft is provided on the output shaft extended from the motor by way of a gear, a driving unit becomes complex and it becomes long in its entire length, resulting in a drawback of unstable operation when operating a motor-operated welding equipment.
In the second prior art, although the length of the driving unit becomes long, the diameter of the motor becomes large because the nut is fixed to the rotary shaft of the motor inside the motor and also the moment of inertia becomes large because the diameter of the nut is relatively larger than the screw of the screw shaft, thereby extending the acceleration and declaration time of electrodes when the electrodes open and close as the motor operates.
The invention has been made in view of the problems of the conventional driving unit of a welding equipment, and it is a first object of the invention to provide a driving unit of a welding equipment capable of reducing the size of the driving unit and reducing the moment of inertia by integrating or substantially integrating a rotary shaft of a motor and a screw shaft so that the driving unit of a welding equipment has an excellent operability.
It is a second object of the invention to provide a driving unit of a welding equipment capable of easily fixing a screw shaft to a rotary shaft by use of fixed means utilizing a friction force without requiring a troublesome operation such as shrinkage fit or cold shrinkage fit.
It is a third object of the invention to provide a driving unit of a welding equipment capable of securing the application of pressure to a workpiece by a pressure application shaft by disposing an elastic body on the axis of the pressure application shaft through which pressure application force exerts.
It is a fourth object of the invention to provide a driving unit of a welding equipment capable of moving a pressure application shaft to a desired standby position when a motor is troubled by forming a machining part for manually turning the screw shaft at the rear end side of the rotary shaft or screw shaft.